DESCRIPTION: There have been significant advances over the last decade in our understanding of the epidemiology, etiology, and treatment of obsessive-compulsive disorder (OCD). Data from older studies suggests that the course of OCD is usually chronic. However, there are significant gaps in the literature regarding the long-term patterns of course and predictors of this disorder. We do not know whether certain subtypes of OCD have a more pernicious course than other subtypes. The impact of OCD on psychosocial functioning over time is another currently clinically relevant area that has not been examined in previous studies. The broad objective of this proposal is to develop a comprehensive picture of the longitudinal course and outcome of OCD using a prospective, longitudinal, observational design to follow 400 subjects with OCD over a period of three to five years. Specific aims are to: comprehensively describe the long-term patterns of course of OCD; identify clinically meaningful predictors of remission and relapse; prospectively describe the amount of psychiatric treatments received; assess the relationship between psychosocial function, quality of life and OC symptom severity over the follow-up period. Using a well-defined method developed by Keller and colleagues for observational studies of anxiety and depression, the study will evaluate 400 consecutive patients with OCD using DSM-IV criteria for the disorder over a three to five year follow-up period. Detailed information on symptom status and severity, functional impairment, quality of life, diagnostic Status and treatments received will be recorded systematically using instruments with proven reliability and validity at yearly intervals. This study will be the first comprehensive prospective observational study of the course of illness in OCD and will be the first study to prospectively determine remission and relapse rates according to DSM-IV criteria. It will provide important new information about longitudinal aspects of treatment and predictors of remission and relapse that will, in turn, help refine data supporting the existence of homogeneous subtypes in OCD.